Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$190.73	4.566%	$199.4387	$199.44	$199.45	$199.40
Purchase #2	$114.58	3.753%	$118.8802	$118.88	$118.90	$118.90
Purchase #3	$172.75	8.588%	$187.5858	$187.59	$187.60	$187.60
Purchase #4	$15.46	13.366%	$17.5264	$17.53	$17.55	$17.50
Purchase #5	$201.63	10.527%	$222.8556	$222.86	$222.85	$222.90
Purchase #6	$117.44	9.522%	$128.6226	$128.62	$128.60	$128.60
Purchase #7	$65.99	9.631%	$72.3455	$72.35	$72.35	$72.30
7 purchase totals =	$878.58		$947.2548	$947.27	$947.30	$947.20